1. Field of the Invention
The present invention relates to a process and a composition for removing residues from the microstructure of an object. The present invention specifically relates to a process and a composition for removing residues such as resists, generated during a semiconductor manufacturing process from a semiconductor wafer surface having a fine structure of convex and concave portions.
2. Description of the Related Art
It is required as one step in manufacturing a semiconductor wafer to remove residues, such as photoresists, UV-hardened resists, X-ray hardened resists, ashed resists, carbon-fluorine containing polymer, plasma etch residues, and organic or inorganic contaminants from the other steps of the manufacturing process. The dry and wet removal methods are commonly used. In the wet removal method, the semiconductor wafer is dipped in an agent, such as a water solution, including a remover to remove residues from the surface of semiconductor wafer.
Recently, super critical carbon dioxide is used as such an agent because of its low viscosity and high diffusivity. According to such properties, cleaning with super critical carbon dioxide provide several advances in the treatment of microstructures, such as high penetration into small areas between microstructures and successfully drying microstructures because of non liquid-liquid interface in the super critical phase.
However, super critical carbon dioxide is not enough by itself to remove several residues from the surface of the semiconductor wafer. To resolve this problem, several additives to super critical carbon dioxide are proposed. As described in the Japanese unexamined patent publication No. 10-125644, methane or surfactant having CFx group is used as an additive to super critical carbon dioxide. In Japanese unexamined patent publication No. 8-191063, dimethylsulfoxide or dimethyl-formamide is used as such an additive. However, based on the inventors' studies, these additives are not always effective for removing residues. Especially, when the cleaning object is like a wafer which consist of low dielectric constant materials, the quality of such wafer decreased after treatments by such process using alkaline compounds and water. This might be occurred because basic compounds and water caused damages on low dielectric constant materials, especially on materials having dielectric constant lower than 4. (hereinafter referred to as low-k materials) Thus, the present invention is objected to provide a novel and effective cleaning without significant damage to the low-k materials.